DESCRIPTION: The hypothesis in this application is that Xath regulates the differentiation of olfactory neurons in Xenopus and functions with another basic-helix-loop-helix (bHLH) gene, NeuroD, to regulate successive stages of olfactory neuron development. The first aim is to use in situ hybridization a immunohistochemistry to determine which cell types express Xath during development and regeneration of the olfactory epithelium and determine whether Xath expression coincides with specific stages in olfactory neurogenesis. The second aim is to overexpress Xath by RNA injection and to determine whether Xa expression is sufficient to promote differentiation of olfactory neuron precursors. The third aim is to perform double in situ hybridization and compare the expression of Xath and NeuroD to see if there is evidence for a functional relationship between these bHLH genes.